The invention relates to a method for driving a plasma display for displaying images.
Document U.S. Pat. No. 2002/0030645 describes a method for displaying images applied to a conventional AC plasma storage display having two plane panels, one front and one rear, enclosing between them a space filled with discharge gas which is partitioned into discharge regions, notably using barrier ribs placed between the panels. The front panel comprises two arrays of coplanar sustain electrodes which are covered with a dielectric layer providing the storage effect. Each electrode of one of the arrays forms a pair with an electrode of the other array. The rear panel comprises an array of address electrodes which are oriented perpendicularly to the sustain electrodes. Thus, in this conventional structure each discharge region comprises three electrodes.
When driving according to the method described in the document U.S. Pat. No. 2002/0030645, within each cell during the sustain phase, matrix discharges, which are formed within the gas-filled space between the panels, trigger longer, coplanar discharges which are formed between the electrodes mounted on the same panel.
Other documents describe analogous driving methods where coplanar sustain discharges are triggered by matrix discharges. Documents U.S. Pat. No. 5,962,983 or U.S. Pat. No. 6,376,995 may be cited for example. The document entitled “Highly luminous-efficient AC-PDP with DelTA Cell structure using new sustain waveform” by Y. Seo et al. (FUJITSU Lab.), published on 22 May 2003 during the International Symposium of the SID (SID Vol. 34/1, pages 137-139, XP001171716), describes a driving method in which the trigger voltage pulses are very short, of the order of 150 ns.
Document U.S. Pat. No. 6,184,848 describes an analogous method of driving applied to a display comprising three coplanar electrode arrays mounted on the same panel, the other panel comprising, as previously, an array of address electrodes. Each cell therefore here comprises four electrodes, of which three are coplanar. The first coplanar electrode only for the trigger, the second for both the trigger and the sustain itself, the third only for the sustain. Within each cell, a trigger, or “narrow-gap”, region between the first two coplanar electrodes which are relatively close together, and a discharge expansion, or “wide-gap”, region between the last two coplanar electrodes, which are further apart, are therefore to be distinguished from each other.
Such a driving method applied to one or the other of these displays allows discharges to be triggered between the sustain electrodes of each pair, even when the gap separating them is wide, without having to increase the voltage of the sustain pulses. Thanks especially to greatly lengthened discharges being obtained between these electrodes, such a driving method allows the luminous efficiency of plasma displays with coplanar sustain electrodes to be significantly improved.
Indeed, in a plasma discharge, the energy efficiency of a positive or pseudo-positive column is much higher than that of a negative glow, which is why there is an interest in designing plasma display structures and in using methods for driving these displays that allow stable operation in this pseudo-positive column regime. However, in a conventional display structure using three electrodes and with the driving method that has just been described, obtaining a positive column plasma by simply increasing the gap between the coplanar electrodes does not lead to a very significant increase in the luminous efficiency. As is explained hereinafter, this difficulty in implementing wide-gap discharges, with a luminous efficiency much higher than that of narrow-gap discharges, can be explained by the close correlation between the discharge formation mechanism and the electrical signals applied to these electrodes.